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What is wind chill and how fast can it cause frostbite?

Pedestrians huddle against snow and a cold wind Monday morning, Feb. 4, 2019, in Seattle. (AP Photo/Elaine Thompson)

(NEXSTAR) – Have you ever looked outside on a winter’s day and thought for sure it couldn’t be that cold, but then you step outside and find yourself feeling pretty cold?

A contributing factor may be wind chill.

Wind chill is the combined effect of temperature and wind on your body. As the wind blows over your body, it causes sweat to evaporate from your skin, cooling you down.

It is the combination of cold temperatures and evaporation that leads to wind chill. 

The faster the wind, the more evaporation occurs, and the temperature drop is more significant. 

Further adding to the chill is the fact that winter air tends to be drier, leaving more room for evaporation. When you add all of this together, windy winter days can produce dangerously cold temperatures. 

The Wind Chill Chart from the National Weather Service shows that it doesn’t have to be super cold, and the wind doesn’t have to blow hard, to give someone frostbite in as little as a half-hour. 

Wind Chill Chart (National Weather Service)

For example, for someone outside when the temperature is around five degrees and the wind is at 35 mph, frostbite can set in after about 30 minutes. If the temperature drops to -5 degrees with the same wind speed, frostbite can set in in about 10 minutes.

This is why you are always cautioned to cover exposed skin to limit the impact from bitter cold wind chills. 

If wind chill can increase the risk of frostbite, can it also affect our homes or vehicles?

Fortunately, no, wind chill does not affect cars, radiators, water pipes, or homes. In other words, inanimate objects don’t suffer from wind chill, at least to the point that it is going to cause problems. This is because they don’t sweat or produce excessive amounts of moisture to evaporate. 

Animals with long fur have an insulating layer between their skin and the harsh elements, diminishing the chilling effect. Still, pet experts do not recommend leaving your dog outside for extended periods of time. If they do need to be outside, you are encouraged to put a jacket on them or booties for their paws.